Character encoding: ASCII and Unicode

Overview

Character sets and codes, 7-bit ASCII and the order of its codes, working out a letter's code from A = 65, why '5' differs from 5, and why Unicode was needed.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   What is a character set?

   Model answer

   A character set is a defined list of characters that a computer can represent. Each character in the set has its own unique binary code.

2. 2

   What is a character code?

   Model answer

   A character code is the number given to one character in a character set. The computer stores the code in binary.

3. 3

   How many bits does ASCII use for each character, and how many characters can it represent?

   Model answer

   ASCII uses 7 bits for each character. Seven bits give 128 codes, numbered 0 to 127.

4. 4

   What characters does ASCII include?

   Model answer

   ASCII covers upper- and lower-case English letters, the digits 0 to 9 and punctuation. ASCII also has control codes such as a new line.

5. 5

   The ASCII code for A is 65. What is the ASCII code for E?

   Model answer

   The code for E is 69. The capital letters run in sequence, so E is four places after A.

6. 6

   The ASCII code for a lower-case a is 97. Which character has the code 100?

   Model answer

   The code 100 stands for the lower-case letter d. The lower-case letters run in order from 97 upwards.

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